Vapor cooled transformers, of the type described within U.S. patent application Ser. No. 843,676 are available as replacements for transformers containing polychlorinated biphenyls as one of the constituents of the dielectric coolant. The vapor cooled transformers utilize the dielectric properties of the coolant to insulate the core and windings of the transformer and the change of state properties of the coolant to transfer the heat from the core and windings to a heat exchanger. In order to compensate for the presence of any adsorbed noncondensable gases, such as air, the heat exchangers employed are substantially larger than the heat exchangers required with comparable rated oil filled units. The dissolved noncondensable gases within the coolant become separated from the coolant within the heat exchanger during the condensation cycle of the coolant. The separated noncondensable gases within the heat exchanger form air pockets within the heat exchanger cooling tubes adversely preventing the coolant from entering some of the tubes. The large size of the heat exchangers associated with vapor cooled transformers assures adequate available area for receiving the coolant for the projected life of the transformer.
The purpose of this invention is to provide vapor cooled transformers having heat exchangers of a reduced size by providing accurate means for determining the presence of air leaks within the transformer and for preventing the accumulation of air both within the transformer and the heat exchanger.